Item Infeed Apparatus and Method for a Palletizer

ABSTRACT

An infeed apparatus includes an item manipulator that orients items such as cases in a desired orientation as determined by a build menu, and a row build apparatus that is synchronized with the manipulator to space items pursuant to the build menu. The manipulator uses a pusher to push items across a friction belt to thereby orient the items, and includes sensors for determining when an item is in an incorrect orientation. The row build receives items from the pusher and is selectively advanced to locate items in a desired relative orientation so that rows of items are built correctly.

TECHNICAL FIELD

The present invention relates to palletizing systems and morespecifically to a case infeed apparatus and method that is used toinsure that cases delivered to a palletizer are delivered in the correctorientation and with the proper spacing.

BACKGROUND

A palletizer is an apparatus that receives and manipulates items, suchas boxes, and places the manipulated articles on pallets inpre-determined positions and orientations in organized rows, layers andstacks to form a stable stack of boxes arranged on a pallet forshipping. There are innumerable devices for palletizing articles, butdescribed in a very general sense all palletizers receive a sequence ofitems and manipulate those items to produce a palletized stack of them.Typically, a completed stack of cartons is shrink wrapped as part of thepalletizing operation in order to finalize the stack for shipping.

Stated in very general terms, a typical palletizer receives a series ofitems, organizes the items into rows, organizes the rows into layers,and generates a stack of layers on a pallet.

Efficient shipping of palletized items calls for efficient stacking ofitems on the pallet to minimize open space within the stack and to helpinsure the stability of the stack to prevent relative movement betweenitems, and ultimately, to insure that the items in the stack arrive attheir destination undamaged. Of course, boxes come in a variety of sizesand many boxes are rectangular with opposed parallel side panels andtherefore have different width and length dimensions. A standard palletis used widely throughout the shipping industry. By varying theorientation and/or pattern of boxes from layer to layer, a stable stackof items may be constructed upon a standard-sized pallet. Accordingly, avariety of “box patterns” have been established for stacking specificbox sizes on standard pallets. By using an established box pattern forgiven rectangular boxes that are to be stacked on a standard pallet, theresult is an efficient and stable stack of the boxes on the pallet thatwill perform well during shipping and handling.

A common palletizing system comprises several components that worktogether to perform the palletizing operation. Boxes are initiallyplaced on an infeed system that delivers the boxes to a row buildsystem. Often the infeed system includes box turning equipment thatorients individual boxes in the correct orientation relative to adjacentboxes for the specific box pattern that is being used. Rows areassembled on the row build system—each row is a set of plural boxesarranged according to the box pattern. A row is transferred by one of avariety of methods from the row build system to a layer building stationwhere plural rows are arranged into a layer. A stack is formed bydepositing a first layer onto a pallet or slip sheet and subsequentlayers are deposited atop the next adjacent lower layer. Layers areadded until the stack is complete. Typically, the palletizing operationsat the various stations run simultaneously to the extent possible toincrease throughput efficiency. As would be expected, there are manyvariations of the equipment used to palletize, and the general themes ofoperation.

Regardless of the equipment that is being used, palletizing requiresefficiency in design and operation of the device. Among other design andoperational criteria, efficiency is often one of the most importantconsiderations. In many applications, time is most critical and apalletizer that more quickly organizes an incoming series of items intoa palletized stack of items represents an advantage by increasingthroughput and thus greater production levels and economic efficiency.

It will be appreciated that mishandling of boxes in the palletizingprocess should be minimized as part of an efficient operation and that apalletizing system must be designed to avoid delivery of boxes to thepalletizer in an incorrect orientation. For example, a box that isdelivered to a palletizer in the incorrect orientation for the specificbox pattern that is being used will cause formation of a defectivelayer. This results in shut down, or at least significant slowdown ofthe entire palletizing sequence and operator intervention is oftenrequired in order to correct the orientation of the mis-oriented box.Unfortunately, delivery of such “out of bounds” boxes—that is, boxesthat are either in the incorrect orientation or which are otherwiseimproperly placed—to palletizing systems continues to be a significantproblem and is the cause of much slowdown in palletizing operations.Moreover, any time operator intervention is required to correct out ofbounds situations presents a safety concern for workers.

There is a need therefore for a palletizing system that insures deliveryof boxes to the equipment in the correct orientation and spacing forwhatever box pattern is being used.

The present invention comprises systems that address the shortcomings ofprior systems.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood and its numerous objects andadvantages will be apparent by reference to the following detaileddescription of the invention when taken in conjunction with thefollowing drawings in which an infeed system and an associated,downstream row build conveyer are illustrated, but in which othercomponents of the overall palletizing system are omitted in order tobest show the invention.

FIGS. 1 through 5 illustrate the infeed system in isolation in order toillustrate the various components of the system. In FIGS. 6 through 24the infeed system and the row build conveyer are illustrated in avariety of situations in order to detail operation of the infeed systemand row build conveyer.

FIG. 1 is an upper perspective view showing the infeed system accordingto the invention in isolation without the other components of thepalletizing system, including the side frame elements shown in place.

FIG. 2 is an upper perspective view of a portion of infeed systemaccording to the invention that is similar to the view of FIG. 1, exceptthe side support frames have been removed on the near side of thedrawing to illustrate the drive systems.

FIG. 3 is an upper perspective view of a portion of the infeed systemaccording to the invention that is similar to the view of FIG. 2, exceptthe upstream components of the infeed system are removed.

FIG. 4 is a top plan view of a selected portion of the infeed system.

FIG. 5 is a side elevation view of one side of the pusher bar systemwith the side framing components removed to illustrate the drive motorsand drive systems.

FIG. 6 is a side elevation view of one side of the pusher bar systemwith the side framing components removed similar to FIG. 5, andillustrating the electro-optical sensors and including boxes on theconveyer belt.

FIG. 7 is a side elevation view of one side of the pusher bar systemshown in isolation.

FIG. 8 is a side elevation view of the opposite side of the pusher barsystem shown in FIG. 7, including the sensors.

FIG. 9 is an end elevation view of the pusher bar system taken along theline 9-9 of FIG. 8.

FIG. 10 is an end elevation view of the pusher bar system taken alongthe line 10-10 of FIG. 8, looking the opposite way of the view of FIG.9.

FIG. 11 is an upper perspective view of the infeed system and row buildconveyer according to the present invention showing two cases on theinfeed system.

FIG. 12 is a top plan view of the infeed system and row build conveyeras shown in FIG. 11.

FIG. 13 is an upper perspective view of the infeed system and row buildconveyer according to the present invention showing three cases on theinfeed system.

FIG. 14 is a top plan view of the infeed system and row build conveyeras shown in FIG. 13.

FIG. 15 is an upper perspective view of the infeed system and row buildconveyer according to the present invention showing two cases on theinfeed system and one case transitioning from the infeed system to therow build conveyer.

FIG. 16 is a top plan view of the embodiment illustrated in FIG. 15.

FIG. 17 is an upper perspective view of the infeed system and row buildconveyer according to the present invention showing three cases on theinfeed system and one case fully transitioned onto the row buildconveyer.

FIG. 18 is a top plan view of the embodiment illustrated in FIG. 17.

FIG. 19 is yet another upper perspective view of multiple cases on boththe infeed system and the row build conveyer.

FIG. 20 is a top plan view of the embodiment shown in FIG. 19.

FIG. 21 is an upper perspective view of the infeed system and row buildconveyer according to the present invention with five cases in variouspositions.

FIG. 22 is a top plan view of the embodiment of FIG. 21.

FIG. 23 is another upper perspective view of the infeed system and rowbuild conveyer according to the present invention.

FIG. 24 is the top plan view of the embodiment of FIG. 23.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS

The invention will now be described in detail with reference to thedrawings. Relative directional terms are used at times to describecomponents of the invention and relative positions of the parts. As anaming convention, the ground plane is considered to be the generallyhorizontal surface on which the apparatus of the present invention ismounted. In all conventional installations, the apparatus is installedon a horizontal floor and the upper surface of the various conveyers,row build layers, layer heads, etc. described herein are also horizontaland thus parallel to the ground plane. Other relative directional termscorrespond to this convention: “upper” refers to the direction above andaway from the ground plane; “lower” is generally in the oppositedirection, “inward” is the direction from the exterior toward theinterior of the apparatus, “vertical” is the direction normal to thehorizontal ground plane, and so on. “Upstream” refers to the directionthat is the opposite of the flow of boxes on the system, and“downstream” is the opposite direction—the direction of the flow ofboxes. The articles that are being manipulated on the palletizerdescribed in this specification are standard boxes; in the industry,boxes are also interchangeably referred to as cases and cartons.

Furthermore, in most of the figures used herein some structures areomitted in order to better illustrate selected components andstructures. This includes framing and support structure and the likeused in palletizing systems. Such environmental components are wellknown to those of skill in the art and need not be described or shown inthe figures to understand the invention.

It is to be understood that the infeed system 10 and the row buildconveyer 100 described herein are used as components of an entirepalletizing apparatus that includes numerous additional systems,including for example a lift deck, a layer head a receiving deck and astretch wrapping station. These components are not illustrated becausethe invention described herein may be used with conventional versions ofthe components. Moreover, versions of these components are described indetail in, for example, U.S. Pat. Nos. 7,736,120; 8,074,431; and8,257,011, each of which is owned by the assignee of the presentinvention and the disclosures of which are incorporated herein by thisreference.

The components and operation of the infeed system are described ingreater detail below. However, with reference to FIG. 1 and brieflydescribed, the infeed system 10 is designed for receiving product thatis to be palletized, for example, output from a production ormanufacturing operation or from a repackaging operation. These so-calledproduction feed areas are located “upstream” of the infeed system interms of product flow. Infeed system 10 includes three general sections:a metered belt, a case turner, and a pusher bar. Each of these sectionsis under the continuous control of a computerized processor, showngenerally at 4, and each section includes item transport conveyers, avariety of motors, sensors and encoders that provide feedback andcontrol information to the processor. Processor 4 is a conventionalmicroprocessor with associated software and systems for completeoperation of the palletizer. Among other things, processor 4 storesplural build menus 5—also referred to herein as “pattern build menus.”As detailed below, each build menu 5 contemplates factors including boxsize, the configuration of boxes in rows, the configuration of rows inlayers, and stack height. The build menu thus ultimately defines thenumber and orientation of boxes in a row, the number and orientation ofrows in a layer, and the arrangement and number of layers in a stack.

The function of the infeed system 10 is to receive cases 12 from theupstream production feed area, manipulate the cases according to thebuild menu that is being used, and control operation of the palletizingsystem according to data from the sensors; when an out of boundssituation is detected, operation of the palletizing system is shut downor otherwise modified to allow the out of bounds condition to becorrected. As another naming convention used herein, all cases shown inthe drawings are identified with the reference number 12. When there ismore than one case 12 shown in a drawing figure, the case that isfurthest downstream is assigned reference number 12 a, the next adjacentupstream case is 12 b, then the next upstream case is 12 c, and so on.

Continuing with the general description of infeed system 10, cases 12are received from the production area and delivered to the infeed system10 where individual cases 12 are indexed there along for presentation tothe remaining portions of the palletizer. As may be appreciated and asis detailed below, infeed system 10 operates to appropriately orient asequence of cases 12 according to a build menu 5 that is programed intoprocessor 4. The build menu 5 includes data relating to box size, rowpatterns and individual box orientations in each row, sequential rowpatterns that interfit to form layer patterns, and layer patterns thatinterrelate to ultimately produce a stable stack of boxes on a pallet.As shown in the figures and as readily recognized, cases 12 are notnecessarily symmetrical in their length and width dimensions. Forexample, with standard rectangular boxes the length and width dimensionsare not the equal. As such, individual boxes 12 in any given row and anyrow in a layer may need to be oriented according to the specificpredefined build menu that takes into account row-by-row variationswithin a layer, and layer-to-layer variations for adjacent layers on astack of boxes 12 deposited on a pallet.

Continuing with the general description of product flow through apalletizer, a predetermined number of cases 12 are conveyed in thedesired and predetermined orientation from the infeed system 10 onto therow build conveyer 100 where the items are accumulated in individualrows. It will be understood that the number of cases in a row and theirorientations relative to one another will vary depending upon the sizesof the items, their dimensions, etc.—that is, the build menu 5 dictatesthe number and relative orientation of cases in a row. With briefreference to FIG. 11, the row build conveyer 100 comprises a conveyerbed 102 that is under control of an encoder feedback motor 103 that isin turn under control of the processor 4. The conveyer bed 102 may be ofany appropriate type of conveyer bed, including for example a driventable top type of chain or plural driven rolls.

Operationally, when a single row of cases 12 has been assembled onto therow build conveyer 100, the cases 12 are transferred together as a rowfrom the row build conveyer 100 onto an upstream row processing devicesuch as a lift deck or layer accumulation area (not shown) with, forexample, a puller bar or other equivalent apparatus such as a pusherbar. The row of cases 12 may be further conditioned as appropriate onwith compaction bars and the like if appropriate once transferred ontothe upstream row processing device such as a lift deck or layeraccumulation area (not shown)

From this point the palletizer uses known components to sequentiallybuild a stack of cases 12 on a pallet according to known techniques.Those components and methods are not elements of the present invention,are known to those of skill in the art, and are thus not detailed here.

With the foregoing as background information, the infeed system 10 usedin the present invention, and its components, will now be described indetail.

With returning reference to FIG. 11, infeed system 10 generally definesa conveyer system that delivers cases 12 from the production feed whereboxes are generated to the row build conveyer 100. The infeed system 10incorporates apparatus and functionality that allows the cases 12 to bepositioned in the correct orientation and with the correct spacing forthe build menu 5 that is being used. Moreover, the infeed systemincorporates feedback systems that detect when a particular case 12 isincorrectly positioned—that is, an “out of bounds” condition—andresponds to such a condition appropriately so that the condition may becorrected either automatically or by operator intervention before adefective row or layer is built. In some out of bounds situations it ismost efficient to stop the system operation and have the operatorcorrect the problem. In other instances it may be possible to correctthe problem with a slowing of the system speed, coupled with some kindof corrective intervention. In either case, it is much safer and quickerto correct a mis-positioned case 12 before a defective layer is actuallybuilt.

Turning now to the series of drawings of FIGS. 1 through 10, infeedsystem 10 comprises three separate components, referred to herein as ametering belt section 14, a case turner section 16 and a pusher barsection 18. Each of these components is independently operable andcontrolled by processor 4. Metering belt section 14 is located at themost upstream portion of infeed system 10, case turner section 16 islocated immediately downstream of and adjacent to metering belt section14 and pusher bar section 18 is immediately downstream of and adjacentto case turner section 16. Each of these three sections that make up theinfeed system 10 is described below beginning with metering belt 14.

As noted, metering belt 14 is located at the most upstream portion ofinfeed system 10 and is designed to receive cases 12 from the productionfeed that is located prior to and upstream of the infeed system 10 interms of product flow. The normal product flow direction of infeedsystem 10 is illustrated with arrow A in FIG. 1, and the arrow thusillustrates the “upstream” and “downstream” ends of the infeedsystem—downstream is the direction the arrow points and upstream is theopposite direction. In FIG. 1 there are five separate cases 12illustrated on the infeed system 10. As noted above, for purposes ofclarity these cases are identified with reference numbers 12 a, 12 b, 12c and so on to identify specific cases.

Infeed system 10 and its three components, metering belt section 14,case turner section 16 and pusher bar section 18 are mounted to andsupported by elongate side frames 20 and 22. The side frames 20 and 22are conventional support members and preferably include footings thatrest on the floor and which allow for vertical adjustment, and bracketsand bracing as appropriate and as understood by those of skill in theart.

Metering belt section 14 is defined by a high friction belt 24 thatextends around upstream and downstream rollers 26 and 28, respectively.At least one of the rollers 26 or 28 is a driven roller that isconnected by a drive belt to an AC motor (neither of which is shown),which is under the control of a variable frequency drive controller.There are numerous types of high friction belts that may be used forbelt 24. One preferred type of belt is a high friction table top chainmeter belt, although as noted, there are many types of belts that willsuffice. The metering belt section 14 is capable of receiving cases 12from the production feed that is immediately upstream of the meteringbelt section. Since the motor that drives belt 24 is under the controlof a variable frequency drive controller and processor 4, the speed ofthe belt may be varied so that the metering belt section 14 is capableof holding back some accumulated cases 12 that are delivered from thesortation area.

Infeed system 10 utilizes several pairs of electro-optical sensorsmounted along the length of the infeed system to monitor the positionand orientation of cases, and in cooperation with the processor controloperation of the components of the system. Each of the sensors iselectrically interfaced with the processor 4 and each is a standardposition sensor that is capable of detecting changes in light—i.e.,interruption of the light beam that is transmitted between the pairedsensors across the conveyer—and convert that change to an electronicsignal that is transmitted to processor 4. Processor 4 includes anencoder algorithm that correlates the electronic signals received fromthe sensors to data correlating to the build menu 5 and otherinformation relating to operation of the system. The sensors are mountedadjacent the infeed system 10 in positions that the light beam betweenpaired sensors is interrupted by boxes 12 as the boxes are conveyed pastthe sensors.

As illustrated, the sensors may be mounted to side frames 20 and 22. Inthis description, sensors in a pair are identified with a referencenumber combined with either the letter “a” for the sensor mounted toside frame 22 and the letter “b” for the other sensor of the pair thatis mounted on the opposite side frame 20. For example, one pair ofsensors is identified with reference numbers 32 a, 32 b and thisconvention is followed throughout this specification. Those of skill inthe art will recognize that the described paired thru beam sensors areonly one style of sensor that can be used with the present invention,and that other types of sensors will work just as well. These include,for example, retro reflective, diffuse beam and other sensor types,which are equally capable of providing input to processor 4.

A first pair of electro-optical sensors 32 a and 32 b is mounted nearthe downstream end of metering belt section 14 on opposite sides of thebelt 24—mounted to side frames 22 and 20, respectively. Both areelectronically connected to processor 4. The sensor 32 a is preferablymounted to frame 22 but may be mounted to any appropriate structure;sensor 32 b is mounted directly opposite sensor 32 a on frame 20. Thesensors are aligned so that a beam of light is transmitted between thetwo sensors—this applies to each pair of sensors utilized in infeedsystem 10 described herein. Sensors 32 a and 32 b define the meteringbelt section 14 controllers that operate in connection with processor 4to stop and start the belt 24; the speed of the belt 24 is regulated byprocessor 4 so that only a single case 12 is indexed onto the caseturner section 16 at a time.

Case turner section 16 is configured to receive cases 12 delivered frommetering belt 14 and to rotate selected cases 12 according to thespecific build menu 5 that is stored in processor 4. In FIG. 1 the caseturner section 16 is shown generically because there are numerous typesof case turners that may be used with the present invention. Forexample, the case turner shown generally at 36 in FIG. 1 could be acaterpillar type of case turner that utilizes one or more differentialspeed belts that have opposing sides that are capable of being moved atdifferent speeds to cause a case on the belts to rotate. This type of acase turner is known in the art and is described generally herein. Thecase turner 36 utilizes a belt 38 of that has opposite sides that arecapable of being driven at different speeds. The belt 38 shown in thefigures is configured as three paired, side-by-side belts (for a totalof 6 belts in the case turner section 16). The belt 38 and itsside-by-side sections are driven by motors (not shown) that are variablespeed motors under the control of the processor 4.

Other types of suitable case turners include deployed arm turners, liftand rotate plate turners and others as known to those of skill in theart. The series of figures of 11 through 24 illustrate a “bump turn”obstruction type of turner.

With reference to FIG. 1 it may be seen that the five cases 12 arearranged in different orientations along the length of infeed system 10.Thus, case 12 e—the most upstream of the cases—is rotated 90 degreesrelative to the case 12 a, the most downstream of the cases. The boxmenu 5 thus may instruct the case turner 16 to have the case 12 arotated by 90 degrees relative to case 12 e, etc. The build menu 5stored in processor 4 provides a signal to the case turning componentsof case turner section 16 instructing actuation of the case turningapparatus when a specific case requires turning according to the patternbuild menu 5.

The function of case turner section 16 is to rotate selected casesaccording to the pattern build menu 5 stored in processor 4.

Operationally, when a single case 12 such as case 12 b in FIG. 1 isindexed onto case turner section 16 from the metering belt 24 theprocessor 4 recognizes whether that particular case needs to be turnedbased on the known orientation of the case as it is indexed onto thecase turner section, and based on the pattern build menu 5. Theprocessor 4 adjusts the speed of metering belt so that the speed of belt38 of case turner section 16 is always moving faster than belt 24 ofmetering belt section 14 so that that the case 12 is always transitionedonto the case turner section with a gap between adjacent cases. Once acase has been transferred from the metering belt 24 onto the caseturning section 16 the metering belt 24 either stops when the next caseis positioned on the metering belt, or continues to run depending on thespacing required in the build menu 5.

In FIG. 1, case 12 d has been handed off from the metering belt sectionto the case turner section 16 and processor 4 has initiated rotation ofcase 12 d relative to case 12 e. The case 12 d is positioned on belt 38at the location on the belt where case turning is done, shown generallyat 41. When this occurs, the motors that drive the belt 38 and which areoperably connected to and under the control of processor 4 initiatesoperation of the case turner 41 to turn case 12 d by 90 degrees.

As noted above, the metered belt section 14 indexes cases onto the caseturner section 16. In practice, the metering belt 24 delivers the casesto the case turner section 16 such that there is a gap between adjacentcases; the amount of the gap varies depending on if a specific caseneeds to be turned or not according to the particular build menu. Cases12 are moved downstream on infeed system 10 and are next transferredfrom the case turner section 16 to the pusher bar section 18.

Although the case turner section 16 and case turner 36 generallyorientates cases 12 reliably, there are instances where the cases arerotated less or more than 90 degrees as needed for the pattern buildmenu 5. The case turner section 16 does not position cases; its onlyfunction is transport cases and turn designated cases when the buildmenu 5 requires turning. For instance, as shown in FIGS. 1 and 2, a case12 b that is leaving case turner section 16 has been rotated less than90 degrees and is thus skewed in its position as it moves down theinfeed system 10 and as it is fed onto the pusher bar section 18, whichis immediately adjacent to and downstream of case turner section 16. Asdetailed below, pusher bar section 18 functions to correct casepositioning as the cases are fed from the pusher bar section onto thenext adjacent section, downstream row build conveyer 100. Moreover,pusher bar section 18 operating in concert and cooperation with rowbuild conveyer 100 insures that cases 12 are precisely positionedrelative to adjacent cases according to the specifications of thepattern build menu 5 on the row build conveyer.

Reference is now made to the series of drawings of FIGS. 2 through 10,which best illustrate the various components of pusher bar section 18 ofinfeed system 10. An endless friction belt 40 extends around an upstreamroller 42 that has its opposite ends 44 and 46 journalled to bearings 48(one of which is shown in FIG. 2). The bearings are suitably attached tothe side frame 20, which is removed in the view of FIG. 2 to illustratethe components of the pusher bar section 18. At the downstream end ofthe pusher bar section, generally identified with reference number 51,endless belt 40 extends around downstream roller 92 that has itsopposite ends journalled to bearings that are likewise attached to theside frame 20 or brackets attached thereto. The upper surface offriction belt 40 between the upstream end and downstream end 51 definesa box supporting zone of the pusher bar section 18 on which boxes 12 aresupported as they are conveyed along infeed system 10 and on the boxsupporting zone. The belt 40 defines the conveyer on which items aretransported on the pusher bar section.

A variable speed belt drive motor 80 is mounted to a bracket 60 belowbelt 40. The belt drive motor 80 is under the control of processor 4 foraccurate control of the motor speed. The belt drive motor 80 isconnected with a drive belt 86 that extends around pulley 82 on thedrive motor 58 output shaft 84 and around pulley 88 that is connected todownstream roller 90. Rotation of output shaft 84 of drive motor 80causes movement of the endless belt 40 of the pusher bar section 18.

Pusher bar section 18 includes one or more pusher bars 70 that extendacross endless belt 40 transverse to the belt travel direction and whichare independently operated from belt 40. In the embodiment illustratedherein there are two pusher bars 70 located approximately equidistantfrom each other along the loop of chains that drives the pusher bars.Each pusher bar has one end 71 attached to a drive chain 72 that extendsin a loop at one side of the belt 40 and its opposite end 73 attached toa drive chain 74 that extends in a similar loop at the opposite side ofthe belt. The drive chains 72 and 74 extend around sprockets that aremounted to the ends of the upstream roller 42 and a downstream shaft 77,respectively. More specifically, geared sprockets 76 are mounted to eachopposite end 46, 48 of upstream roller 42 and identical geared sprockets78 are mounted to the opposite ends of downstream shaft 77 such that thesprockets 76 are longitudinally aligned with corresponding sprockets 78.The drive chain 72 extends around sprockets 76 and 78 on one side ofendless belt 40 and the drive chain 74 extends around sprockets 76 and78 on the opposite side of the belt. As noted, in the embodimentillustrated herein, there are 2 pusher bars spaced approximately evenlyalong the path defined by the chains. A pusher bar motor 58 that ismounted to bracket 60 has a pulley 59 mounted to its output shaft 66. Adrive belt 62 extends around pulley 59 and a pulley 52 that is attachedvia shaft 77 to geared sprocket 78 that is aligned with upstream gearedsprocket 76 and meshes with drive chain 72. As with belt motor 80,pusher bar motor 58 is a variable speed motor that is an encoderfeedback motor under the control of processor 4 for accurate control ofthe motor speed. Both the operation and speed of pusher bar motor 58 areunder the control of processor 4, and are independent of the operationand speed of belt drive motor 80.

As illustrated in various figures, and especially the side elevationview of FIGS. 6, 7 and 8, as pusher bar motor 58 operates, rotation ofoutput shaft 66 causes movement of drive chain 72 such that pusher bars70 travel from the upstream end of the pusher bar section 18 toward thedownstream end along the upper surface of the belt 40 (i.e., in thecounterclockwise direction in FIG. 6). Drive chains 72 and 74 transitionaround the geared sprockets 78 on the downstream shaft 77 and travelalong a return path below belt 40, over a lower sprocket 98 (see FIG. 6)and then transitioning around upstream roller 42 on sprockets 76 in acontinuous path around the pusher bar section 18. The pusher bars 70 areclosely spaced from the surface of belt 40 as they travel over the topof the belt as best illustrated in, for example, FIG. 5.

An apron or dead plate 53 is located immediately downstream of theroller 90 of belt 40 and is positioned so that cases 12 are smoothlydelivered from belt 40 and/or pusher bars 70 onto the dead plate 53. Thefunction of the dead plate is to define a smooth transitional zone forcases 12 transitioning from pusher bar section 18 onto roller conveyer100, and also to function as a high friction stationary plate acrosswhich the cases are pushed by the pusher bars to assist with squaring ofthe trailing edges of the cases against the pusher bars. Similarly thefriction belt 40 can slow or stop during pusher bar engagement with acase to further increase drag against the case bottom to assist casestraightening by the pusher bar that completes transition of casesacross pusher bar section 18.

Ideally, when a case 12 is being transported from case turner section 16to pusher bar section 18, drive belt motor 80 adjusts its output speedso that the speed of endless belt 40 matches the speed of belt 38. Thecase 12 is thus transferred from case turner section 16 to pusher barsection 18 with the conveyer belts associated with each section—belt 38and endless belt 40, respectively—travelling at the identical speed.This assures a smooth and accurate transition of the case 12 from onesection to the next adjacent section. However, the belts 38 and 40 maybe traveling at differential speeds. In any event, sensors 94 a and 94 bdetect the presence of a case 12 entering pusher bar section 18 when theleading edge 12′ of the case interrupts the light beam transmittedbetween the sensors. The case 12 continues to move in the downstreamdirection until it is fully transitioned onto the endless belt 40 of thepusher bar section.

A first pair of upstream electro-optical sensors 94 a and 94 b ismounted near the upstream end of pusher bar section 18 on opposite sidesof belt 40 and a downstream pair of sensors 96 a and 96 b is mountedadjacent to the downstream end of the pusher bar section, over the rowconveyer 100. The sensors 94 and 96 are electrically interfaced withprocessor 4. Like sensors 32, sensors 94 and 96 are position sensorsthat detect changes in light—i.e., interruption of the light beam thatis transmitted across the endless belt 40—and coverts that change to anelectrical signal that is transmitted to processor 4.

Operation of pusher bar section 18 will be described next. As a case 12moves downstream from case turner section 16 the leading edge 12′ of thecase passes through sensors 94 a and 94 b. The belt 40 is at this pointbeing driven by drive motor 80 at speed X. Once the trailing edge 12″ ofthe case passes by sensors 94 a and 94 b the controller 4 recognizesthat a case is located on pusher bar section 18 and the controllerinitiates operation of pusher bar drive motor 58 to thereby causemovement of the pusher bars 70 in the direction moving from upstreamtoward downstream. The pusher bars 70 are driven at a speed that isrelatively greater than X—that is, the pusher bars 70 are travellingover belt 40 faster than the case 12, which is stationary on the beltand thus traveling at the same speed as the belt. As the pusher bar 70engages the trailing edge 12″ of case 12, which as noted is travelingmore slowly than the pusher bar, the case is propelled forward (i.e.,downstream) by the pusher bar over the relatively more slowly movingbelt 40. The controller may adjust the speed of belt 40 to insure thatthe belt is travelling more slowly than the pusher bar, and may eventemporarily halt rotation of the belt. As the case 12 is propelleddownstream by the pusher bar 70 over the relatively more slowly moving(or stationary) belt 40, the case 12 will square against the pusher bardue to friction between the bottom of the case and the belt 40 and alsothe dead plate 53 if the case has moved that far downstream. That is,the trailing edge 12″ of the case aligns parallel to the pusher bar 70and the relatively more slowly moving, or static, belt increases thefriction between the bottom of the case and the belt to enhance squaringof the case relative to the pusher bar. The length of the portion of thebelt 40 that the pusher bar 70 transports the case 12 across does notneed to be the full length of the pusher bar travel distance becauseonce the pusher bar engages the case, the bar may provide the entireforward (i.e., downstream) transport of the case. As the now squaredcase 12 continues downstream the case is transported past paired sensors96 a and 96 b, which are positioned slightly downstream of end 51 of thepusher bar section 18.

Stated in another way, the pusher bars 70 move in a circular path (i.e.,counterclockwise in the view of FIG. 6) and when the bars are movingover the upper surface of belt 40 i.e., the box supporting zone, theyare moving in the direction from upstream toward downstream—arrow A inFIG. 1. With a case 12 positioned fully on belt 40—that is, with thecase completely supported on the belt so that the leading edge 12′ andtrailing edge 12″ are both within the limits of the case supportingsurface consisting of belt 40 and dead plate 53—and with movement of thebelt either slowed or stopped, a pusher bar 70 comes up from behind thecase—i.e., approaches the case 12 from the upstream direction as thepusher bar travels from upstream toward downstream. The pusher bar ismoving along its continuous path at a speed that is greater than thespeed of belt 40, if the belt is moving at all. As such, the pusher barmakes contact with the trailing edge 12″ of the case. As the pusher bar70 engages the case from behind, it pushes the case 12 in the downstreamdirection against the friction between the case and the high frictionbelt 40, which is traveling slower than pusher bar 70 or which iscompletely stopped, and or dead plate 52. This causes the rear edge ofcase 12—that is, the trailing surface 12″, to align itself parallel tothe pusher bar 70. If case 12 is skewed on belt 40 so that its flattrailing surface 12″ is in any orientation other than parallel to thelongitudinal axis of pusher bar 70, the case is shifted and aligned withthe pusher bar as the case is pushed across the friction belt by thepusher bar.

With the case size information stored in the processor at build menu 5,the dimension of the case 12 passing by the sensors 96 a and 96 b isknown and therefore the orientation of case 12 is known. If arectangular case is conveyed past a pair of sensors such that the longside of the box is parallel to the direction of conveyer travel (arrowA, FIG. 1), and the relatively shorter side of the box is transverse tothe direction of travel, the sensors will detect a box length thatactually corresponds to the true box length. In other words, if the boxis situated on the belt so that the leading edge 12′ first trips thesensor beam and the trailing edge 12″ (as determined by the position ofthe pusher bar 70), the processor 4 recognizes box length datacorresponds to a box being in a given orientation. But if the box isskewed on the belt so that the beam of light is first broken by a cornerof the box (rather than an end of the box) and thus the diagonallyopposed corner being pushed by pusher bar 70, the length valuedetermined by the processor is greater than that of a correctly positionbox. In the case of a skewed box, the corner that first passes throughthe light beam is the leading edge. Of course, if a case is symmetricalin its width and length dimensions (i.e., a square case) there is nodistinction between the leading and trailing edge dimensions regardlessof which side of the box is the leading edge, although the diagonaldirection is longer than the length and width dimensions. As such, itwill be appreciated that the “leading edge” may be a side of a case, acorner of the case, or some other surface of the case and the leadingedge thus is the surface of the case that breaks the light beam.

As noted previously, drive motor 58 is an encoder feedback motor underthe control of controller 4. The encoder feedback function allows thecontroller to recognize the position of pusher bar 70 along its travelpath. Said another way, the position of the pusher bar 70 iselectronically evaluated throughout its travel path so that when theleading edge 12′ of a case passes sensors 96 a and 96 b, the orientationof the case may be evaluated by processor 4 and compared to the expectedvalue. If the detected case length value (i.e., the distance between theleading surface 12′ at sensors 96 a and 96 b and the trailing surface atpusher bar 70) is equal to the expected case length value (i.e., thepredetermined length value for that case in build menu 5), or is withina predetermined acceptable range of values for the expected case lengthvalue stored in build menu 5, the processor determines that the case isproperly oriented. As explained above, cases that are not properlyturned 90 degrees (i.e., not squared against pusher bar 70) present alonger length because they are measured on a diagonal—the distancemeasured from the leading surface 12′ to the trailing surface 12″ isgreater across the diagonal than the distance between side edges. If thecase length value as determined by the distance between the leading edge12′ at sensors 96 a and 96 b and pusher bar 70 is not within thepredetermined expected case length value or range, indicating amiss-turned case, the processor 4 may then stop for operatorintervention.

The position of pusher bar 70 as determined by encoder feedback providesa known position of the trailing edge 12″ of a case 12 and transportspeed. This allows the row build conveyer 100 to be in a position toproperly receive the case 12 as it is delivered from the pusher barsection 18 to the row build conveyer 100. As detailed below, before acase 12 is transferred from the pusher bar section 18 onto to the rowbuild conveyer, the row build conveyer may be operated to create a gapbetween adjacent cases as required according to the build menu 5.Alternately, the speed of the row build conveyer 100 may be synchronizedwith the pusher bar 70 speed so that adjacent cases 12 are immediatelynext to one another on the row build conveyer without a space betweenadjacent cases.

Sensors 96 a and 96 b define the case 12 length measurement sensors inconjunction with the pusher bar 70 position and the expected case lengthbased on build menu 5 in processor 4. As the case leading edge 12′ of acase 12 is transported past sensors 96 a and 96 b the controller 4 willhave data corresponding to the length of the case, based on the locationof pusher bar 70 and the position of the leading edge 12′ of the case12, and compares the length dimension derived from data from the sensorsto the length dimension stored in the controller based on expectedlength from the build menu 5. The distance between the pusher bar 70 andthe paired sensors 96 a and 96 b is a function of the encoder basedpositioning value of bar 70 when the sensors are broken. As such, whenthe leading edge 12′ of the case 12 breaks the beam of light betweensensors 96 a and 96 b the case length is determined and compared to theexpected value.

If the dimension of case 12 measured by the position of pusher bar 70and the leading edge 12′ of the case as measured by sensors 96 a and 96b is different from the expected dimension value stored in controller 4based on the build menu 5, controller 4 recognizes that the case isskewed or otherwise incorrectly positioned and the controller can stopoperations and/or alert the operators.

The pusher bar continues to drive a properly straightened case 12downstream and over dead plate 53 and onto the next downstream sectionof the palletizer, which is the row build conveyer 100. Row buildconveyer 100 also utilizes an encoder feedback motor 103 that is underthe control of processor 4.

The infeed system 10 and row build conveyer 100 comprise at least threedifferent methods to effectively position cases 12 on row build conveyer100—that is, to position the cases properly according to the build menu5. Each of the three methods confirms that the case 12 is properlyturned on the row build conveyer—as noted above, if a case 12 isimproperly turned so that it is skewed, turned when it should bestraight or straight when it should be turned based on the break of thelight beam between sensors 96 a and 96 b by leading edge 12′ and pusherbar 70 position based on encoder feedback, the controller either shutsthe system down so that the problem may be corrected, or otherwisesignals the operators that intervention is required.

The three methods for proper induction of cases 12 onto row buildconveyer 100 are as follows:

-   1) When the pusher bar 70 reaches the encoder value representing the    count where the leading edge 12′ of the case 12 should break the    sensors 96 a and 96 b where the case begins to transition onto row    build conveyer 100, row build conveyer 100 is energized and the case    transitions onto the row build conveyer in a relatively synchronized    manner. When the case 12 has been fully transitioned onto the row    build conveyer 100, the row build conveyer stops if no gap between    adjacent cases is required, or runs for a predetermined time or    encoder pulse value based on the build menu 5 to create a gap in    anticipation of the next following case 12;-   2) The row build conveyer 100 is able transport the case 12 thereon    so as to create a space that will be in preparation for receipt of    the next following case 12, including any required gap by    immediately after full receipt of a case 12 rapidly indexing the    case length if the cases are to be adjacent to each other or case    length plus a gap. In this manner the pusher bar 70 essentially    pushes the case 12 onto a static surface row build conveyor 100    (i.e., over dead plate 53) and then the row build conveyor 70 is    energized by controller 4 to create a gap in anticipation of the    next case needs; and-   3) A combination of the two above methods where the row build    conveyor 100 always runs on some distance after receipt of a case 12    so that when the leading edge 12′ of a case 12 is transitioning onto    row build conveyor 100 the pusher bar 70 is initially pushing the    case onto a static or just-starting-to-run row build conveyor 100    surface, but the row build conveyor is equal to the speed of pusher    bar 70 speed and indexes the programed amount the next case would    require for proper position including a gap, if any. This method    allows the row build conveyor 100 to effectively index a spaced    amount as would be required by the next case, but the speed of    motion of the row build conveyor 100 is not necessarily synchronized    with the speed of the pusher bar 70 speed. The initial gap provides    a space for the pusher bar 70 to transition the case onto row build    conveyor 100, which is then absorbed as the two conveyors ultimately    synchronize positions based on each other's encoder values.

It will be appreciated that the foregoing system and methods allow forthe system—that is, controller 4—to accurately recognize the position ofthe trailing edge 12″ of a case 12 as the case is transferred from thepusher bar section 18 onto the row build conveyer 100—the encoderposition of the pusher bar 70 when it stops moving the case 12 towardthe row build conveyer 100 thus registers the position of the trailingedge 12″. This allows the row build conveyer 100 to index a programmablevalued based on the requirements of the build menu 5 before the nextcase 12 is induced onto the row build conveyer. As noted, in someinstances the build menu will call for the next case 12 to beimmediately adjacent the prior downstream case so that there is no gapbetween the two cases 12. In other instances, the build menu will callfor a gap between the cases. In the latter case where a gap is requiredthe row build conveyer will create the gap by continuing to run apredetermined amount of encoder pulses to create the desired gap betweenthe cases. Those of skill in the art will recognize that a timer may beused in lieu of encoder pulses to achieve the desired positioning ofcases on the row build conveyer.

A brief summary of important points in the foregoing description includethe following:

-   a) the leading edge 12′ of cases 12 turned (or not turned, as the    case may be) by the case turner section 16 break the beam of light    between sensors 94 a and 94 b, thereby causing operation of a pusher    bar 70 to engage the trailing edge 12″ of the case 12;-   b) the pusher bar 70 moves faster than the belt 40 and squares the    case 12 by pushing the case over a more slowly moving, slowing, or    static high friction surface defined by the belt 40 and or dead    plate 53;-   c) the leading edge 12′ of case 12 breaks the beam of light between    sensors 96 a and 96 b and the controller compares the dimension of    the case by comparing the distance between the leading edge 12′ and    the trailing edge 12″—the later by the position of pusher bar 70 via    encoder feedback motor 80—and the controller affirms that the case    is in the correct position relative to expectation based on encoder    values programmed into the build menu. If the measured dimension is    different from the expected dimension, the system stops or otherwise    signals that intervention is required;-   d) when the leading edge 12′ passes between sensors 96 a and 96 b    the pusher bar section 18 initiates transition of the case 12 onto    the row build conveyer according to one of the three methods    described above to insure that the case is properly positioned on    the row build conveyer according to build menu 5 requirements.

The foregoing description of the operation of infeed system 10 may beillustrated with the series of drawings of FIGS. 11 through 24, whichillustrate a variety of different case numbers on the infeed system 10.As noted above, the case turner 16 shown in FIGS. 11 through 24 is abump turn type of turner 200. Case turner 200 is a conventional turningdevice that includes an obstruction 202 that extends partially acrossthe path of cases 12 being transported along the case turner section 16,and a deflector arm 204 that is operably under the control of controller4. Operation of this type of turning device will be familiar to those ofskill in the art and may be derived by comparing FIGS. 15 and 16. InFIG. 15, the deflector arm 204 is in its home or non-deployed position.In this position, case 12 a strikes obstruction 202 as the case is movedfrom upstream toward downstream, thus causing case 12 a to rotate in theclockwise direction. In FIG. 16 the deflector arm 204 is deployedoutwardly from its home position. As case 12 b is transported along theinfeed system 10 with the deflector arm 204 deployed, the case isshifted laterally toward the center of the belt as it slides along thedeflector arm, but the case is not rotated on the belt.

With reference now to the series of figures of 11 through 24, theoperation and synchronization of infeed system 10 and row build conveyer100 will be detailed by the sequential nature of the drawings. Thedrawings of FIGS. 11 through 24 are paired and show sequential stepsinvolved in operation of the infeed system and row build conveyer. Thus,FIG. 11 is a perspective view and FIG. 12 is a top plan view of FIG. 11and is the first in the series of steps; FIG. 13 is a perspective viewand FIG. 14 is a top plan view of FIG. 13 and these drawings representthe following step in the sequence, and so on.

FIGS. 11 and 12 show two cases on infeed system 10. Case 12 b is beinghanded off from the metering belt section 14 to the case turner section16 and case 12 a is being turned by the bump turner 200, and morespecifically, by bumping into the obstruction 202 that is in the path ofthe case (i.e., the deflector arm 204 is in its home, non-deployedposition).

In FIGS. 13 and 14 another case 12 c has been added onto the meteringbelt section 14 and the most downstream case 12 a of the three cases hasbeen partially turned by the bump turner 200 and fully transported ontothe pusher bar section 18 in a slightly skewed position. In other words,the trailing edge 12″ of case 12 a is not parallel to the pusher bar 70,which may be seen approaching the trailing edge 12″. As noted above,when the trailing edge 12″ passes sensors 94 a and 94 b, processor 4recognizes that a case 12 is fully on the pusher bar section 18 and thusactivates movement of the pusher bars 70 and concurrent slowing (orstopping) of belt 40.

FIGS. 15 and 16 is the next sequential view of the cases shown in FIGS.13 and 14. In FIGS. 15 and 16 case 12 c has been engaged by pusher bar70 and has been squared against the pusher bar. Accordingly, case 12 cis properly oriented. In these figures, the leading edge 12′ of case 12a is just passing sensors 96 a and 96 b. As such, processor 4 is at thistime evaluating the orientation of case 12 a (by the value representingthe distance between the leading edge 12′ and the position of pusher bar70 at the trailing edge 12″). Because the case 12 a is squared againstthe pusher bar, the length value will be consistent with the expectedvalue (unless the case 12 a, which is rectangular, were actually turned90 degrees from what was expected according to the build menu 5, inwhich case the measured value would be different from the expectedvalue). It will be understood that depending on the orientation of acase 12, the “leading edge” 12′ may be defined by either a side of acase (where, for instance, the case is squared properly on the belt) ora corner of the case (where, for instance, the case is skewed). The sameapplies to the trailing edge. As such, the terms “leading surface” and“trailing surface” are sometimes used to describe the portion of a casethat is “leading” or “trailing.”

Also illustrated in these figures is case 12 b being turned byobstruction 202 of bump turner 200, and deflector arm 204 moved into itsdeployed position so that case 12 a will not bump into obstruction 202and will therefore not be turned.

Moving to FIGS. 17 and 18, case 12 a is fully supported on row buildconveyer 100, which has been stopped by processor 4 as case 12 b isbeing squared on the pusher bar section 18 by pusher bar 70 and pushedby the pusher bar over the slowed or stationary belt 40 and dead plate53. The next immediately upstream case 12 c is being shifted laterallyby deflector arm 204, but not turned, and case 12 d is ready fortransfer from metering section 14 onto case turner section 16.

FIGS. 19 and 20 show the next sequential step and illustrate theoperation of row build conveyer 100 according to the specific build menu5. Here, the build menu has called for cases 12 a and 12 b to beimmediately next to one another in the row that is being built on therow build conveyer, without a gap between the two cases. The row buildconveyer is thus not operated in the time between the FIGS. 17 and 18,and the time shown in FIGS. 19 and 20. As case 12 b is pushed by pusherbar 70 onto row build conveyer 100, the conveyer is stationary so thatcase 12 a is moved by case 12 b being pushed against it. Case 12 c isnearly but not fully on pusher bar section 18—the trailing edge 12″ hasnot passed sensors 94 a and 94 b so the pusher bars 70 are not yetactivated, and case 12 d is about to be turned by bumping intoobstruction 202. A case 12 e has been added to metering section 14.

In FIGS. 21 and 22 the row build conveyer 100 has been operated totransport cases 12 a and 12 b in the downstream direction to create agap between case 12 b and the following case 12 c, which is being pushedonto the row build conveyer 100 by pusher bar 70, and a gap between case12 c and the following case 12 d. Case 12 e is being turned byobstruction 202 and case 12 e is being transported onto the case turnersection 16 from the metering belt section 14.

FIGS. 23 and 24 are the last in the series of sequential illustrations.In these figures, two new cases (12 f and 12 g) have been placed on thecase turner section 16 and the metering belt section 14, respectively.Case 12 e is being turned on the case turner section 16.

The sequential operation of the infeed system 10 with row build conveyer100 thus allows for building of a row on the row build conveyer withcases 12 in the desired orientation and with adjacent cases eitherimmediately adjacent one another, or with desired gaps, all determinedby the build menu 5.

It will be appreciated by those of skill in the art that certainequivalent modifications may be made to the structures described hereinwithout changing the nature or scope of the invention. For instance, thepusher bars 70 shown and described herein travel along a path thatroughly follows the path of the conveyer belt 40—the pusher bars cyclebeneath the belt as they rotate. However, the pusher bars could just aswell descend from above the belt to engage cases on the conveyer. Andwhile the illustrated embodiments described above are discussed in termsof manipulating standard boxes, the inventions described herein may beused to manipulate any number of other items including, for example,bags, bundles, trays and the like that may be palletized.

While the present invention has been described in terms of preferred andillustrated embodiments, it will be appreciated by those of ordinaryskill that the spirit and scope of the invention is not limited to thoseembodiments, but extend to the various modifications and equivalents asdefined in the appended claims.

1. A method of assembling rows of items in a palletizer, each itemhaving a leading edge and a trailing edge, the method comprising thesteps of: a. delivering a first item to a first conveyer; b. engagingthe trailing edge of the first item with a pusher and aligning the firstitem so that the trailing edge is parallel to the pusher; c. deliveringthe first item with the pusher to a row accumulator; and d. determiningthe position of the trailing edge of the first item on the rowaccumulator by detecting the position of the pusher.
 2. The methodaccording to claim 1 including the steps of: a. delivering a second itemto the first conveyer; b. engaging the trailing edge of the second itemwith the pusher and aligning the second item so that the trailing edgeis parallel to the pusher; c. delivering the second item to the rowaccumulator and determining the position of the trailing edge of thesecond item by detecting the position of the pusher.
 3. The methodaccording to claim 2 wherein the step of delivering the second item tothe row accumulator includes the step of positioning the second item onthe row accumulator in a desired position relative to the first item. 4.The method according to claim 3 wherein the step of positioning thesecond item on the row accumulator in a desired position relative to thefirst item includes positioning the second item so that the leading edgeof the second item abuts the trailing edge of the first item.
 5. Themethod according to claim 3 wherein the step of positioning the seconditem on the row accumulator in a desired position relative to the firstitem includes positioning the second item so that the leading edge ofthe second item is spaced apart from the trailing edge of the firstitem.
 6. The method according to claim 1 wherein the row accumulatorfurther comprises a second conveyer and the step of delivering the firstitem with the pusher to a row accumulator includes advancing the firstitem on the second conveyer to a desired position thereon.
 7. The methodaccording to claim 6 wherein the second item delivered to the rowaccumulator with the leading edge of the second item spaced from thetrailing edge of the first item.
 8. The method according to claim 6wherein the second item is delivered to the row accumulator with theleading edge of the second item abutting the trailing edge of the firstitem.
 9. The method according to claim 1 including the step of turningthe first item.
 10. The method according to claim 1 wherein the firstitem is turned prior to engaging the trailing edge thereof.
 11. Themethod according to claim 1 including providing a motor to drive thepusher and wherein the position of the pusher is detected by an encoderin the motor.
 12. The method according to claim 11 wherein thedimensions of each item is known and the position of the leading andtrailing edges of each item are determined by the detected position ofthe pusher.
 13. A method of assembling rows of items in a palletizer,each item having a leading edge and a trailing edge, the methodcomprising the steps of: a. orienting a first item in a predeterminedrotational orientation; b. engaging the trailing edge of the first itemwith a pusher and aligning the first item so that the trailing edge ofthe first item is aligned with the pusher; c. delivering the first itemto a row accumulator with the pusher; d. detecting the position of thepusher to thereby determine the position of the trailing edge of thefirst item; e. orienting a second item in a predetermined rotationalorientation; f. engaging the trailing edge of the second item with thepusher and aligning the second item so that the trailing edge of thesecond item is aligned with the pusher; g. with the pusher, deliveringthe second item to the row accumulator in a desired position relative tothe first item.
 14. The method according to claim 13 wherein the desireposition of the second item is determined by a detected position of thepusher.
 15. The method according to claim 13 wherein the second item ispositioned on the row accumulator such that the leading edge of thesecond item is spaced apart from the trailing edge of the first item.16. An apparatus for assembling rows of items in a palletizer, each itemhaving a leading edge and a trailing edge, comprising: a conveyer fortransporting one or more items; a pusher driven by a motor, the pusheradapted to push the one or more items on the conveyer and deliver theone or more items to a row accumulator in a predetermined locationthereon, the pusher adapted to engage the trailing edge of at least oneitem of the one or more items so that the pusher and the trailing edgeof the at least one item are aligned; and pusher location means fordetecting the position of the pusher.
 17. The apparatus according toclaim 16 in which the pusher location means is defined by an encoderassociated with the motor.
 18. The apparatus according to claim 16 inwhich the conveyer travels at a first speed and the pusher travels at asecond speed that is greater than the first speed.
 19. The apparatusaccording to claim 16 wherein the row accumulator comprises a secondconveyer and a motor for driving the second conveyer.
 20. The apparatusaccording to claim 19 wherein the second conveyer is adapted totransport the one or more items to a predetermined position prior to asubsequent one or more items being delivered to the second conveyer. 21.A method of assembling rows of items in a palletizer, each item having aleading surface and a trailing surface, the method comprising the stepsof: a. delivering a first item to a first conveyer; b. engaging thetrailing surface of the first item with a pusher; c. delivering thefirst item with the pusher to a row accumulator; and d. determining theposition of the trailing surface of the first item on the rowaccumulator with a sensor associated with the position of the pusher.22. The method according to claim 21 including the steps of: a.delivering a second item to the first conveyer; b. engaging the trailingsurface of the second item with the pusher c. delivering the second itemto the row accumulator and determining the position of the trailingsurface of the second item with the sensor associated with the positionof the pusher.
 23. The method according to claim 21 including the stepsof: a. determining a dimension of the first item by determining thedistance between the detecting a position of the leading surface of thefirst item on the row accumulator and comparing said detected positionof the leading surface with the determined position of the trailingsurface; and b. comparing the determined dimension to an expecteddimension.